Pump



March 31, 1931. FERR|S ET AL 1,798,198

ATTRNEY March 31, 1931.` W FERRlS ET AL 1,798,193

ATTORNEY March 3,1, 1931: A wFERRls ETAL 1,798,198

Filed Mal-o h 4, ),926 '5 Sheets-Sheet 3 ATTORNEY 5 SheetsfSheet 4 ih m u PUMP W. FERRIS ET AL Filed March 4I 1926 March 31, 1931.

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\ll l; v `NM\ MMIIIIIHMHHT 'Ii' il March 3l, 1931. w. FERRls E'r AL 1,798,198

PUMP

' Filed March v4, 1926 5 Sheets-Sheet 5 /06 08 /ao //5 C L e ATTRNEY n manica Mar. 31, 1931 UNITED STATES PATENT oFFicE PUMP Application filed March 4, 192e. serial No. 92,135.

This invention relates to pumps for. use primarily in variable speed hydraulic transmissions.

One object of the present invention is the provision in a variable displacement pump of improved regulating means so const-ructed and arranged as to eect an extremely accurate control of pump displacement particularly within that region Where pump displacement is relatively small.

Another object is the provision in a. variable displacement pump of a reversing valve coordinated with the displacement regulating means in such manner as to obtain a smooth variation in liquid flow from Zero to a maximum in either direction.

Another object is the provisionof operating mechanism for the valve and displace-v ment regulating means capable of giving the valve a relatively fast motion and the regulating means a relatively slow motion in the vicinity of zero displacement.

Another object is the provision of improved overload relief mechanism capable of effecting a prompt reduction in pump displacement in the event of excessive hydraulic pressures.

Another object is the provision of improved iuid actuated mechanism for effecting and controlling the operation of the stroke change mechanism.

Another object is the provision of a novel arrangement and dimensioning of ports within the pump to insure complete filling of the pump cylinders during the suction stroke thereof.

Other objects and advantages will appear from the following description of an illustrative embodiment ofthe present invention.

In the drawings Figure 1 is a longitudinal sectional view of a pump constructed in accordance with the present invention. This view is taken substantially along the line 1-,1 of Figure 2.

Fig. 2 is a transverse sectional view taken substantially along the line 2-2 of Figure 1.

, Figs. 3 and 4 are views illustrating different operating positions of parts 'shown in Figure 2.

Fig. 5 is a view of the overload relief mechanism 4in action.

Fig. 6 is a horizontalsectional view taken substantially along the line 6 6 of Figure 2.

Fig; 7 is a longitudinal sectional View of the mechanism for operating and controlling the pump regulating means.

Fig. 8 is a sectional view taken substanhtially along'the line 8-8 of Figure 7 Figs. 9 and 10 are sectional views taken substantially along the line 9--9 of Figures 7 and 8, showing the parts in different operating positions.

Fig. 11 is an elevational view, partly in section of the pump unit.

Fig. 12 is an enlarged sectional View of the pump pintle, diagrammatically illustrating the relation between it and the cylinder ports of the pump.

Figure 13 is a view, similar to Figure 12, illustrating a modified form of pintle.

The pump selected for illustration is shown wholly enclosed within a main casing 10, which serves as a reservoir for the working fluid, preferably oil. The normal oil level is indicated by the line X-X. The casing is closed at the ,top by a movable cover 11 and at one end by an auxiliary housing 12 removably fixed thereto. The housing 12 Constitutes a support for the driver 13 of the pump and for the drive shaft 14 which are secured together to rotate as a unit. The driver and shaft are journalled in spaced bearings 15 and 16 in the housing and are driven by any appropriate means such as a pulley 17 fixed to the outer end of the shaft.

The pump shown, is a variable displacement pump of the rotary, multiple piston type. It comprises a cylinder barrel 18 having a hub 19 suitably bored as at 20 and fitted for rotation upon the projected end 21 of a pintle 22 within the driver 13. The cylinder barrel is provided with a series of cylinder bores 23 radially disposed about the central bore 20, and adapted `to register successively with gashes 24 and 25 formed in the circumferential surfaces of the pintle 22 during the rotation of the cylinder barrel thereon. A piston 26 is closely fitted for reciprocation in each cylinder bore 23, and each carries a crosshead 27. The driver 13 carries adjacent its periphery, a series of tangential reaction plates 28 removably fixed in opposed grooves 29 formed in the peripherial walls 30 of the driver. Interposed between each cross-head 27 and cooperating reaction plate 28, is a load transmitting means of such character that all thrusts imposed upon each cross-head are applied normal thereto. In the pump shown, the transmitting means comprises a pair of rollers 31 and 32 having free rolling contact with and between the opposed faces of each cross-head and cooperating reaction plate. A positioning cage 33 associated with each pair of rollers 31 and 32 which are rotatable therein, is freely movable between the cooperating cross-head and reaction plate, within limits defined by a retaining pin 34 secured in the reaction plate 28 and a projection 35 on the cross-head, both loosely engaging a slot 36 in the roller cage 33.

The pintle 22 is anchored in a horizontal arm 38, rockablysupported at one end upon a horizontal shaft 39, extending transversely of the casing 10, and fixed at its opposite ends in appropriate hollow bosses 40 forming integral parts of the side walls of the casing. The anchored end 41 of the pintle is formed with gashes 42 and 43. Gash 42 communicates with gash 24 through a pair of longitudinal passages 44 in the pintle, and gash 43 communicates with gash 25 through a similar pair of passages 45. Gash 42 communicates with a passage 46 in the arm 38 and gash 43 communicates with upper and lower passage 47 and 48 in the arm. The arrangement is such that when the pump is rotated in a counter-clockwise direction (Figs. 2 and 11) and the arm 38 is in the lower neutral position of Figures 1 and 2 with'ft'heaxis of the pintle 22 colncident with the'axis ofthe driver 13 and drive shaft 14, the pistons 26travel about the pintle 22 without reciprocating in the cylinder bores 23 and pump displacement is zero. By raising the arm 38 toward the position shown in Figures 3 and 4, the axis of the pintle 22 is adjusted upwardly toward-the eccentric position of Figure 11, causing the pistons 26 to reciprocate within the cylinder bores 23 during their travel about the pintle. This causes liquid to be discharged from the cylinder bores 23 successively into the gash 24, through passages 44, and gash 42 into the passage 46, liquid from the passage 47 or 48 returning to the cylinder bores through the gash 43, passages 45, and gash 25. The rate of this liquidow is, obviously dependent upon the extent of reciprocation of the pistons Within the cylinder bores which is determined by the distance that the axis of the pintle has been shifted from coincidence with the axis of the driver. Although, as will hereinafter appear, the arm 38 may, under some condition, assume a position lower than that shown in Figures land 2, its normal throw is between that position and the upper position of Figures 3 and 4, so that under normal working conditions the. direction of liquid flow in the passages 44 and 45 is as above described. Whenever the arm 38 is depressed below the neutral position of Figures l and 2 however, the axis of the pintle is depressed below that of the driver, and the How of liquid in the passages 44 and 45 is reversed, so that the pump then receives liquid from passage 46 and delivers into passage 47 or 48.

The opposite ends of the shaft 39 are bored out tc form passages 49 and 50 (see Fig. 6), which may be connected through appropriate couplings 5l to the opposite sides of a hydraulic circuit. The circuit may include any type of hydraulic motor. Passage 49 is in open communication through ports 49 with an annular chamber 52, formed in the arm 38 and surrounding the shaft 39. Passage 50 is in open communication through ports 53 with a similar chamber 54 surrounding the shaft. A reversing valve of appropriate form controls communication between the passages 46, 47 and 48 and chambers 52 and 54. In this instance a piston valve 55,

mounted for lengthwise reciptrocation in a bore 56, extending vertically through the arm 38 is employed for this purpose. As shown in Figures 2, 3, and 4, the bore 56 is provided with five spaced annular grooves `l57, 58, 59, 60 and 61. Groove 57 communicates with-passage 47, groove 58 communicates with chamber 52 through a passage 62, groove 59 communicates with passage 46, groove 60 communicates with chamber 54 through' a passage 63, and groove 61 communicates with passage 48. The piston valve has four piston heads 64,65,66 and 67. Heads 64 and 67 constitute permanent closures for the upper and lower ends 'of the bore 56. Head "65 controls communication between grooves 57 and 58 and between grooves 58 and 59, and is preferably of a thickness less than that of groove 58, so that when the valve is in the neutral position of Figure 2, li uid may How from groove 59 around hea 65 past groove 58 and into groove 57, and the pump is by-passed or short-circuited. Head 66 controls communication between grooves 59 and 60 and between grooves 60 and 61, and is preferably somewhat thicker than the groove 60, so that when the valve is in neutral position this groove is completely 'covered and the passage 63 is completely blocked so as to prevent a liquid iow in the hydraulic circuit.

The arrangement is such that slight movement of the valve 55 downwardly toward the position shown in Figure 3, blocks communication between grooves 58 and 59 and between grooves` 60 and 61, and communication isestablished between grooves 59 and 60, so that liquid delivered bythe pump through passage h46 is free to pass through passage 63,

chamber 54, ports 53, and passage in the shaft 39 to one side of the hydraulic circuit. Also grooves 57 and 58 communicate so that liquid from passage 49 in the shaft 39 is free to pass to the pump through ports 51, chamber 5,2, passage 62, grooves 58 and 57 and passage 47. Similarly slight movement of the valve upwardly from-the neutral position of Figure v2 toward the position of Figure 4 blocks communication between grooves 57vand 58 and between grooves 59 and 60, and opens communication between grooves 58 and 59 and between grooves 60 and 61. Liquid delivered by the pump through passage 46 passes through passage 62 into the passage 49 in the shaft 39, and liquid from passage 50 is free to pass through passage 63 and 48 back to the pump.

The arm 38 is adjusted between the lower neutral position of Figure 2 and the upper full line position of Figure 3 or 4 by mechanism which will cause a relatively slow, but accurate, movement of the arm in the vicinity of its lower neutral position, anda relatively fast movement in the vicinity of its upper position. `The mechanism shown for the purpose is essentially a toggle mechanism and includes a crank arm 68 fixed to a rock shaft 69, and connected to the end of an extension 70 of the arm 38 through appropriate linkage 71. Shaft 69 is mounted to rock about a xed axis as will be hereinafterl in the extension 70 of the arm 38. A crosshead 76 is connected to the end head 7-2 through a pair of tension rods 77, anchored at their lower ends in the end head and passing loosely through the cross-head. The rods 77 are maintained under tension by a coiled spring 78, maintained under compression between the cross-head and an end plate 7 9 on the upper ends of the rods. A pair of heavy, stiff springs 8O on rods 70 between the heads 72 and 79 maintain the heads in spaced relation and serve as apcushioning means, permitting limited vibration of the arm 38 under periodic pulsationsin pump reaction on the pintle 22 supported thereby. The cross-head is bored out to receive a crank .pin 81 on the crank arm 68. With the crank change in the vposition of arm 38, the rate of movement of the arm 38 increasing as the crank approaches either of its upper positions.

In the pump shown provision is made for coordinating the adjustment of the valve with the adjustment of the pump, so as to effect a relatively rapid movementl of the valve when the pump is in the vicinity of zero displacement position, thereby moving the valve in either direction from neutral far enough to give ample port openings before the pump delivery becomes large. is accomplished in this instance by connecting the valve through suitable linkage to the crank arm 68 in such man ner as to obtain a rapid movement of the-valve 'as the crank passes through neutral position. The valve 55, as. shown, ,is provided with a control stern 82, having a head- 83, grooved to receive a slide block 84. The block carries a trunnion 85 engaged in one'arrn of a bell-crank 86, rockably supported upon a bracket 87 carried by the larm 38. The other arm-of the bell-crank is connected through a horizontal link 88 to the end of the crank arm 68. It will be noted that the link 88 extends laterally from the crank 68, so' that the link responds instantly to any slight movement of the crank from neutral position, and effects a corresponding movement of the valve.

With the crank in the neutral position of- Figure 2, pump displacement is zero, and the valve 55 is in neutral, pump delivery passage 46 is open to the return passage around the valve head 65, so that the pump is-short-circuited (as hereinabove explained), and the passage 63, leading to the passage 50 in the shaft 39, is blocked/by thel valve head 66. Under these conditions there can be no flow in the hydraulic circuit. Vhen the crank 68 is swung toward the left, toward the position shown in Figure 3, the valve is lowered This and the pump. delivers liquid into and i through the passage 50 in the shaft 39 and receives liquid from the passage 49, so as to cause a flow of liquid in the circuit at a rate dependent upon the distance the arm 38 has been lifted by the crank 68. When the crank is swung in the opposite direction toward the position shown in Figure 4, the valve 55 is raised, and the pump delivers liquid into and through passage 49 in shaft 39 and receives liquid from passage 50. The direction of flow in the hydraulic circuit is thus reversed, the rate of flow again depending upon the distance the arm 38 has been lifted by the crank. I

The crank 68 may be actuated and controlled by any appropriate means. Mecha-- nism for this purpose is shown in Figures 7 to 10. IThis mechanism includes a casing 89 mounted in fixed position in the end wall 90 of the main casing 10. The casing 89 encloses a rotary piston 91 closely fitted at one end for rotation within a reduced portion of the casing, and at theother end within a sleeve 93 fixedl within the casing and forminga closure therefor. Two fixed abutments 94 and 95 within the casing divide the annular space surrounding the piston into two segmental chambers 96 'and 97. Two vanes 98 and 99, carried by the piston, project into chambers 96 and 97, respectively, and are closely fitted against the walls thereof. A rotary valve 100 is closely fitted within a central longitudinal bore 101 in the piston. Two series of assages 102 and 103 lead from the bore 101 tirough the wall of the piston to the opposite sides of the vane 98. Two series of passages 104 and 105 lead from the bore* to the opposite sides of the vane 99.

vThe opposite sides of the valve 100 are cut -away to form chambers 106 and 107 within the bore, and the top and bottom surfaces of the valve are channeled to form chambers 108 and 109 Within the bore. Chambers 108 and 109 communicate through ports 110 and 111 with a longitudinal passage 112 through the valve. The chambers 106 and 107 open at one endiinto an annular groove 113, surrounding the valve, and communicating through ports 114 with an annular groove 115, surrounding the piston 91. The groove 115,. is supplied with fluid under pressure through aV pipe 116 leading from an appropriate pressure source. The valve 100 is controlled by a stem 117 fixed thereto and extending from the casing 89, an appropriate handle 118 being fixed to the outer end of the stem. The rock shaft 69, hereinabove referred to, carrying the crank 68, is fixed at one end Within the rotary piston 91 so as to rotate therewith, and is provided with a longitudinal passage 119 in open communication with the passage 112 in the valve 100.

The'arrangement is such that the chambers 106 and 107 are maintained flooded with liquid under pressure supplied from pipe 116 through groove 115, ports 114, and groove 113, and chambers 108 and 109 are always open to exhaust through ports 110 and passages 112 and 119, the liquid escaping through passage 119 into the main casing 10. With the valve 100 in the intermediate position shown in Figures 7, 8 and 9, the ports 102, 103, 104, and 105 are'blocked so that there can be no flow of liquid into or out of either of the segmental chambers 96 and 97. The piston 91 is thus held in the intermediate position shown, and the crank 68 is in neutral. To effect movement of the crank 68 from the neutral position of Figure 9 into the position of Figure ,10, the valve 100 is rotated clockwise into the- .dotted line position of Figure 9. Rotation of 4the valve in such direction uncovers the sev- -eral ports 102, 103, 104 and 105, so that orts 102 and 104 areopen to the pressure c am- -be'is 107 and 106, respectively, and ports 103 and-105are1-opened to the exhaust chambers 108 and 109,-respectively. The pressure thus applied to the left side of vane' 98 and to the.

right side of vane 99 causes the piston 91 to rotate clockwise, turning the shaft 69 and A piston 91 is thus rotated through an angle equal to the angle through which the valve 100 has been turned, and then automatically comes to rest due tothe re-blocking of the ports 102, 103, 104 and 105. Similarly when the valve 100 is rotated counter-clockwise ports 103 and 105 are opened to the pressure chambers 106 and 107, respectively, and ports 102 and 104 are opened to the exhaust chambers 108 and 109, so-that pressure is applied to the right side of vane 98 and to the left side of vane 99, causing the piston 91, and consequently the shaft 69 and crank 68, to rotate counter-clockwise, through an an le corresponding to the angle through which the valve 100 is turned.

Relative rotation between the valve 100 and piston 91 is preferably limited by any appropriate means such as a pin 120, which projects radially from the valve into a segmental depression 121 in the end face of the piston. i

In the pump shown fluid under pressure is supplied to the pipe 116 froma standard type of gear pump 122 mounted within the auxiliary housing 12. (See Figure 1.) The gear pump shown comprises the usual pair of intermeshing gears 123 and 125, disposed within a casing 126 and driven by the shaft 127. The shaft 127 is driven by a"gear 128 fixed thereto and meshing with a gear ring 129 fitted on the drive shaft-14, and fixed to the driver 13 so as to rotate therewith. The gear pump receives liquid from the bottom of the main casing 10, through a channel 124, and forces this liquid through a connection, not shown, to the pipe 116.

Overload relief mechanism is providedv for effecting an automatic reduction 1n ump d1 s placement when the pressure in the ydraulic circuit fed by the pump exceeds a predetermined degree. Although this may be accomplished in vvarious ways, the mechanism shown in Figures 2 and 5, has proven entirely successful for the purpose, and operates to effect a very prompt change in pump displacement. This mechanism comprises a lunger 130, closelyfitted for reciprocation 1n the end head 72 of the expansible llnkage 71. The plunger 130 projects into a chamber 131 within the boss` 73 and bears against the lower face of the cross-head 76. The chamber 131 communicates, through a port 132, with an' annular groove 133, surrounding the pin 74. The groove 133 is in open communication with the discharge passage 46 of the pump through a tubeM 134, leading from the upper end of a vertical passage 135 inthe arm 38, the passage 135 communicating with passage 46 through al port 136. The liquid pressure in chamber 131 thus corresponds at all times to thc pressure in passage 46,`which of of course corresponds to the pressure within the hydraulic circuit fed by the pump. To illustrate th'.` functioning of this mechanism' let it he assumed that the crank arm 68 has been swung into the position shown in Figures 4 and 5 so that the arm 38 has been raised and the pump is delivering liquid through passage 46 into the passage 49 in shaft 39, leading to one side of the hydraulic circuit. This flow will continue at the rate determined by the setting of the crank 68, until the pressure in the circuit, and consequently in the passage 46 and chamber 131, has increased to a point which is suiiicient to force the plunger 130 outwardly, against the resistance of the spring 78, causing a separation of the heads 72 and 76 as indicated in Figure 5. This causes a lowering of the arm 38 toward the neutral dotted line position of Figure 4 and pump displacement is accordingly reduced.

The initial compression in the spring 7 8, is suficient to prevent this action of th plunger 130 until the pressure in chamber 131. corresponding to pump pressure, eX- ceeds a predetermined limit for normal working pressures, so that at pump pressures working below this limit, the heads 72 and 76 are maintained in the spaced relation indicated in Figures 2, 3, and '4 and the position of arm 38 is delinitely determined by the position of crank 68. When this limit is exceeded, however, and the plunger 130 is forced outwardly, the arm 38 is lowered, and the spring 78 further compressed. the spring 78 is further compressed it offers a progressively increasing resistance to the action of the plunger 130, so that the arm is lowered to a point at which the increased pressure in the spring 78 is balanced against the hydraulic pressure applied to the plunger 130. The effect of this arrangement is to divide the functioning of the pump vinto two zones, a normal working zone, in which the ump may be made to deliver accurately controlled volumes of liquid irrespective of 'ari ations in pump pressures within the normal limit, and an overload zone in which the overload mechanism in response to pressures in excess of this limit, operates directly on the pump to promptly modify the rate of delivery thereof. The plump.v when functioning in the overload zone, is thus capable of handling excessive loads without excessive power demands on the prime movcr, and when these loads are reduced to normal the pump is automatically returned to its normal operating zone in which accurate control of pump delivery is restored.

This overload relief mechanism also comes e5 into play to afford a smooth reversal of the hydraulic circuit and motor driven thereby, i

position shown in Figure 3, so that the pump l is delivering a large volume of liquid through passage 46 into passage 50, and receiving liquid at an equal rate from passage 49 through passage 47. Then suppose that the crank 68 is swung suddenly through neutral position toward the position of Figures 4 and 5. The liquid flowing toward the pump from passages 49 would be suddenly met by the liquid discharged by the pump through passage 46, causing a sudden building up of pressure in passage 46. This pressure would also be increased and maintained for an interval of time, due to the'inertia reaction of the motor driven by the circuit. This pressure acting on the plunger 130 would cause a separation of the heads 72 and 76 to such an extent as to lower the arm 38 below the neutral position of Figure 2 thereby reversing the pump and permitting a reversal in the direction of iow within the .passage 46. This condition would prevail 'until 4the motor, driven by the circuit, came t9 rest. As the motor approached a condition of rest the reversed flow in the passages would progressively decrease with corresponding reduction in pressure permitting the plunger 130 to slowly retract, also permitting the heads 72 and 76 to approach each other, and thereby raise the arm 38 through its neutral position toward the position of'Figure 4. As the arm 38 passed through neutral, the pump would again deliver liquid through passage 46, causing a reversal of flow in the hydraulic circuit and a vreversal of the motor driven thereby.

Pumps of the type described are frequently used-in connection with closed hydraulic circuits of varying volumetric capacities such that the volume of oil delivered by the pump into one side of the circuit may be greaterV or less than the volume received by the pump from the other side of the circuit.` Since it 1s necessary that the pump receive as much oil as it delivers, provision must be made, in such installations, tov compensate for such variations in volume. In thisinstance two check valves 137 and 138 are associated with the passage 48 leading to the take side of the pump. These valves are submerged in the body of liquid within the casing 10. Valve 137 comprises a casing 139 open at one end through a passage 140 with passage 48 and open at the other end througha port 141 with the body of liquid within the casing 10. V valve element 142, yieldably retained in closed position by a spring 143, prevents upward liow of liquid into the passage 48, but permits escape of liquid from said passage when the pressure therein is suiiicient to overcome the pressure of spring 143. The other end toa passage 145 leading into passage 48 adjacent the pintle 22, and open at its lower end through a ort 146 with the body of liquid in casing 10. valve element 147 is retained by gravity in closed position so as to prevent the escape of liquid from passage 48 therethrough. This valve however permits a free flow of liquid upwardly therethrough whenever the` pressure in passage 48 falls .below atmospheric. Thus valve 137 permits the escape of any excess liquid returned to the pump and valve 138 permits a free How of liquid to the pump to compensate for any deficiency in the volume of liquid returned thereto from the circuit.; f

Although the Huid pressure in delivery passage 46 is usually greater than that in the return passage 47 or. 48, there are some conditions of operation in which thepressure in the return passage 47 or 48 is greater than that in the delivery passage. This is true whenever the motor in the hydraulic circuit tends to run faster than is warranted by the rate of liquid delivered by thepump, as, for instance, when pump delivery is suddenly re'- duced, the inertia of the motor is resisted by the liquid in the return side of the circuit causing a building up of pressure within the return passage 47 or 48. The tension of the spring 143 determines the degree of pressure available within the return passage 47 or 48 to meet this resistance. If this pressure is eX- ceeded, fiuid is discharged through the valve 137 into the casing 10. Under such conditions of operation the pump may not receive suicient liquid from the return passage to maintain the delivery side of the circuit flooded. Provision is therefore made for admitting liquid into the delivery passage 46 under such conditions. This is accomplished by the use of a check valve 148 at the lower end of the passage 135. This valve is substantially a duplicate of valvev 138 and is submerged within the body of oil within the casing 10. The arrangement is such that oil from passage 135 cannot escape into the casing 10, but oil from the casingis free to pass upwardly into the passage 135fand passage 46 under suction therein. t

It willbe noted that the rotating parts of the pump, including the driver 13 and the cylinder barrel 18, are disposed belo'w the level of the body of liquid within the main casing 10. In order to avoid the power losses from churning of the oil that would otherwise result from actual contact of these rotating parts with this body of oil, these parts are enclosed within an appropriate housing 150. The housing shown comprises a circular end plate 151, spaced from the closed end 152 of the auxiliary housing 12, and a peripheral wall 153. The end plate 151 is provided with an opening 154 through which the pintle 22 projects and of ample size to permit adjustment of the pintle as above described.

The opening 154 is covered by a ange 155 on the arm 38, an ap ropriate acking rin 156 being interposedlbetween t e plate an flange to prevent admission of oil in any considerable #quantities intothe housing. Oil

that leaks into the housing through the pintle.

22 or otherwise is permitted to escape throu h an appropriate opening 157 formed in t e top of the housing (see Fig. 2) through which the oil is thrown by the centrifugal action of the rotating parts of the pump. The housing is thus maintained substantially free from oil.

In pumps of the type described some difficulty has been experienced in maintaining the several cylinders thereof filled with the working fluid. At the normal operating speeds of from six to nine hundred revolutions per minute, the suction stroke of each piston occupies a very limited interval of time, and it is rather diicult to insure complete filling of the cooperating cylinder within this brief period. Figures 11 and 1,2 illustrate a novel arrangement and propor- 4tion of parts designed to overcome this difficulty. During rotation of the driver 13 and cylinder barrel 18 in the direction of the arrow, each piston 26 is producing an outward suction stroke during its circular travel from the upper dead center position, indicated in dotted lines at A in Figure 12, to the lower .dead center position, indicated in dotted lines, at B; and during its circular travel from position B to position A each piston is producing an inward working stroke. In the pintle shown the upper land or bridge portion 158, between the upper ends of the gashes 24 and-25 (hereinafter referred to as the pressure bridge) is disposed to the rightof the position A, and is thus advanced wlth respect to the direction of rotation; and the lower land or bridge portion 159, (hereinafter referred to as the suction bridge) is disposed to the right of the position B, and is thus retarded with respect to the direction of rotation. That is, each cylinder bore 23 crosses the pressure bridge 158 slightly before the inward stroke of its cooperating piston has been completed, and each cylinder bore crosses the suction bridge 159 slightly after the inward stroke of cooperating piston has begun. /Gash 25, which feeds the cylinders with oil, is thus longer than gash 24, which receives oil from the cylinders, so that thecylinder bores are open to the filling gash 25 a reater length of time. A better opportunity or filling the cylinders is thus provided.

.,Furthermore, due to the retarded position of high pressure of the liquid within the receiving gash 24.

It will also be noted from an inspection of Figure 12 that the face ot' each bridge 158 and 159 is somewhat narrower than the cooperating opening to each cylinder bore 23, so that each cylinder bore 13 in passing over each bridge is opened to one of the gashes before communication with the other gash has been blocked by the bridge; With this arrangement each cylinder bore is always open to one or the other of the gashes, so that, although the piston is in motion as the cylinder bore crosses the bridge, there is no danger of creating excessive pressures that might otherwise occur in the cylinders if the body of oil were trapped therein while crossing a bridge. Furthermore, this relation between the bridges and cylinder openings avoids-a sudden transition in pressure as each cylinder passes from communication with the low pressure oil in gash 25 into communication with the high pressure oil in gash 24.

To further assist in the complete filling of the pump cylinders the return passages in the pintle 22 are made somewhat larger than the discharge passages 44, as indicated in the pintle shown in Figure 13. The enlarged passages 45 permit an easier flow of liquid to the gash 25.

Various changes may be made in the embodiment of the invention hereinabove specitically described without departing Jfrom the invention as defined in the appended claims.

Ve claim:

1. The combination with a variable displacement pump, of valve mechanism for reversing the flow of fluid discharged by said pump, and unitary means for varying pump displacement and for operating said valve mechanism.

2. The combination with a variable displacement pump, of valve mechanism forreversing the flow of fluid discharged by said pump, a control element, means responsive to movement of said element for varying pump displacement, and means responsive to movement of said element for operating said valve mechanism.

3. The combination with a variable displacement pump, of a valve mechanism for controlling the direction of flow of liquid delivered by said pump, a control element, means responsive to movement of said element for varying pump displacement from zero to a maximum, and means responsive to movement of said element for operating said valve mechanism to reverse the direction of flow of liquid delivered by said pump.

4. The combination with a variable displacement pump, of valve mechanism for reversing the flow of fluid discharged by said pump, a control element, means responsive to movement of said control element in either direction from neutral to increase pump displacement, and means for operating sai valve mechanism in accordance with the direction of movement of said element.

5. TheI combination with a variable displacement pump, of valve mechanism for reversing the flow of fluid discharged by said pump, a roclrable control element, means connected with said element Jfor increasing pump displacement upon movement of said clement in either direction from neutral position` and means connected with said element for operating said valve mechanism in one direction or the other upon movement of said element ineither direction from neutral position.

6. The combination with a variable displacement pump, of a valve mechanism for directing the flow of fluid discharged by said pump, a control element, displacement varying means responsive to movement of said element for effecting a relatively slow variation in pump displacement in the vicinityof zero -l displacement position, and valve operating means responsive to movement of said element for effecting a relatively rapid adjustment of said valve mechanism in the vicinity of zero displacement position.

7. The combination with a variable displacement pump, versing the flow of fluid discharged by said pump, means for varying pump displacement, and means automatically operable simultaneously with said displacement varying means for shifting said valve in either direction from neutral position when pump displacement is increased fromzero.

8. The combination with a variable displacement pump, of valve mechanism for reversing the flow of fluid discharged by said pump, toggle mechanism operable to vary pump displacement, and means coacting with said toggle mechanism for operating said valve mechanism.

9. The combination with a variable displacement pump, a valve mechanism for directing the flow of fluid discharged by said pump, toggle mechanism including two pivotally connected levers, means operable upon said toggle mechanism to cause said levers to simultaneously produce an end thrust and a side thrust, means responsive to the end thrust of said levers for varying pump displacement, and. means responsive to the side thrust of said'levers for operating said valve mechanism..

10. The combination with a variable displacement pump, of a member rockable to vary pump displacement, valve mechanism in said member for reversing the flowY discharged by said pump, means for rocking said member to vary pump displacement, and means for operating said valve to reverse the fluid How.

of valve mechanism for reof fluid 11. The combination with a variable displacement pump, of a member rockable to vary pump displacement, valve mechanism in said member for reversing the flow of fluid discharged by said pump, means for rocking said member, and means connecte-d with said last named means for operating said valve mechanism.

12. The combination with a variable dis: placement pump, of a member movable to vary pump displacement, Huid passages in said member connected with said pump, a reversing valve in said member associated with said passages, and means for simultaneously operating said member and valve to vary the rateand direction of fluid flow in said passages.

13. The combination with a variable displacement pump, of a shaft, fluid passages in said shaft, a rockable member on said shaft having passages communicating with said first named assages, respectively, said member being adjustable to vary pump displacement, a valve in said member controlling communication between said last named passages and said pump, and means for adjusting said member and said valve to vary the rate and direction of fluid How in said passages.4

14. The combination of a` variable displacement pump, of a shaft having separate passages in the opposite ends thereof, a roekable member on said shaft adjustable to vary pump displacement, passages in said member connected with said pump and communicating, respectively, with the passages in said shaft, and means for adjusting said member to regulate pump displacement. y

15. The combination with a variable displacement pump, of a shaft having a pair of fluid passages therein, a rockable member on said shaft adjustable to vary pump displacement and having passages connecting said first named passages with said pump, a control element, and means responsive to movement of sai d element for effecting a relatively slow adjustment of said member in the vicinity of zero displacement position and a relatively rapid adjustment of said member in the vicinity of maximum displacement position.

16. The combination with a variable displacement pump, of a member adjustable to vary pump displacement, a control element, and means responsive to movement of said element for effecting a relatively slow adjustment of said member in the vicinity of zero displacementposition and a relatively rapid adjustment of said member in the vicinity of maximum displacement position.

17. The combination with a variable displacement pump, of a member adjustable to vary pump displacement, and means including a rocking element operable to effect a relatively slow adjustment of said member 1n the vicinity of zero displacement posltion and a relatively rapid adjustment of said inemgrec, and fluid ber in the vicinity of maximum displacement position.

'18. The combination with a variable displacement pump. of a member adjustable to vary pump displacement, and toggle mechanism for operating said member slowly in the vicinity of zero displacement position and rapidly in the vicinity of maximum displace- 4 ment position.

19. The combination with a variable displacement pump. of a member movable to vary pump displacement. power means for actuating said member operable to positively determine the position of said member at pump pressures below a predetermined degree, and overload mechanism responsive to pump pressures in excess of said degree for automatically adjusting said member independently of said actuating means.

20. The combination with a variable displacement pump. of a member movable to vary pump displacement, power means for actuating said member. means operable at pump pressures below a predetermined degree for rendering said member responsive to movement of said actuating means. and overload mechanism responsive to pump pressures in excess of said degree for adjusting said member independently of said actuating means.

21. The combination with a variable displacement pump. of a member movable to vary pump displacement, actuating means for said member, longitudinally adjustable connections between said means and member operable at pump pressures below a predetermined degree to render said member responsive to movement of said means, and means responsive to pump pressures in eX- cess of said degree for adjusting said connections to thereby adjust said member.

22. The combination with a variable displacement pump. of a member movable to vary pump displacement. power means for actuating said member, longitudinally adjustable connections between said means and member, means responsive to pump pressures in excess of a predetermined degree for adjusting said connections, and resilient means for preventing adjustment of said connectionsat pump pressures below said degree.

23.` The combination with a variable displacement pump. of a member rrovable to vary pump displacement, fiuid actuated meansconnected with said member for positively determining the position thereof at pump pressures below a predetermined deactuated means operable directly on said member for moving the same in response to pump pressures in excess of said degree.

24. In a variable displacement pump the combination of a member movable lo vary pump displacement, fluid actuated means for adjusting said-member, a valve for controlling the application of fluid pressure to said member, and overload mechanism responsive to pump pressures in excess of a predetermined degree for adjusting said member independently of said valve.

25. In a variable displacement pump the combination of a member movable to vary pump displacement, Huid actuated means for moving said member, including adjustable connections between said means and member through which said member normally responds to the action of said means, a valve `for controlling the application of iuid pressure to said means, and means responsive to pump pressures for adjusting said connections to move said member in response to pump pressures. Y

26. In a variable displacement pumpthe combination of a member movable to vary pump displacement, a fluid actuated element for moving said member, a valve for controlling the application of fluid pressurey to said element, and means responsive to pump pressures for varying the eiect of said element on said member.

27. The combination with a'variable displacement pump, of a member movable to vary pump displacement, a valve for directing the flow of iiuid discharged by said pump, means for adjusting said member and valve to regulate .the rate and direction of said fluid flow, and means responsive to the pressure in said luid How for adjusting said member.

28. The combination with a variable displacement pump, of a member movable to vary pump displacement, a'valve for directing the iiow of iiuid discharged by said pump, unitary means for simultaneously adjusting 'said member and valve to regulate the rate and direction of said iiuid iiow, and means for adjusting said member independently of said valve.

29. The combination with a variable displacement pump of a member movable to vary pump displacement, a rockable element, an expansible link connecting said element and member through which said member is madeto respond to movement of said element, and means responsive to pump pressure for expanding said link.

30. A self contained pump mechanism comprising a rotary liquid impeller, discharge and. return passages hydraulicly connected therewith, means for regulating the displacement ofsaid impeller to thereby regulate the rate of iiow in said passages, a casing enclosing said impeller and providing a liquid reservoir, means associated with said casing for connection with a hydraulic circuit, a reversing valvenontrolling communication between -said passagesand said last named means and operable, to reverse the iow in the circuit, separate passages connecting said first named passages with said reservoir and a check valve in each of said last named passages.

31. A selfcontained pump mechanism comprising a rotary liquid impeller, discharge and return passa es hydraulicly connected therewith, means ir regulating the displacement of said impeller to thereby regulate the rate of flow in said passages, a casing enclosing said impeller and providing a liquid reservoir, means associated with said casing for trolling the application of Huid pressure thereto.

33. In a variable displacement pump the1v combination of a mem er movable to vary pump displacement, a fluid actuated rotary element for actuating said member, and a valve rotatable with respect to said element for controlling theapplication of iuid pressure thereto to eifect rotation ofsaid element thru an angle corresponding to the rotation of said valve.

34. In a variable displacement pump the combination of a member movable to vary pump displacement, a uid actuated rotary elementfor actuating said member, a valve rotatable with respect to said element for controlling the application of iuid thereto to eiect rotation of said element through an angle corresponding to the rotation of said valve, and means for limiting the rotation of said valve relative to said element.

35. In a variable displacement pump the combination `of a member movable to vary pump displacement, a rotary piston for actu-- ,valve and piston fore ecting rotation of said piston through an angle corresponding to the angle of rotation of said valve. 36. In a variable displacement pump the combination of a member movable to vary pump displacement, a cylinder having fixed abutments therein, a piston in said cylinder having vanes between said abutments, passages in said piston leading to opposite sides otsaid vanes, respectively, anda valve cooperating with said passages for controlling the application of iiuid pressure therethrough, to thereby eiiect rotation of said piston through an angle corresponding tothe angle of rotation of said valve, and operating connections between said piston and member. 37. In a variable displacement pump the combination of a member movable to vary pump displacementya Huid pressure source, a rotaryvalve, a rotary element actuated from said source through an angle corresponding to the angle of rotation of said valve, and operating connections between said element and member.

38. -In a variable displacement pump the combination of a member movable to vary pump displacement, a rotary valve, a fluid actuated rotary element controlled by rotation of said valve, a member actuated by and rotatable with said fluid actuated element, and operating connections between said rotary member and said first named member.

39. In a variable displacement pump the combination of a member movable to vary pump displacement, actuating means therefor, operating connections between said actuating means and member. through which said member is made torespond to said actuating means, and cushioning means within said connections permitting limited vibration of said member under periodic pulsations in pump reaction thereon.

40. In a variable displacement pump the combination of a member movable to vary pump displacement, actuating means therefor, means responsive to said actuating means for accurately determining the position of said member, and cushioning means within said last named means permitting limited vibration of said member under periodic fluctuations in pump reaction thereon.

41. In a variable displacement pump the combination of a membermovable to varyl pum displacement, actuating means for said mem er, means responsive to pump pressures for actuating said member independently of said actuating means, and cushioning means permitting limited vibration of said member under periodic uctu'ations in pump reaction on said member independently of said actuating means or said pressure responsive means.

42. In a pump the combination of two relatively rotatable members, a series of cylinders in one of said members, pistons working in said cylinders, a discharge port and return port in the other of said members c0- operating with said cylinders, each cylinder adapted to communicate; with said discharge port during the pressure stroke of its cooperating piston and with said'return port during the suction stroke of its piston, said ports and cylindersbeing so related that communication is established between each cylinder and sai .l return port before its cooperating piston reaches the end of its pressure stroke.

43. In a pump the combination of two relatively rotatable members, a series of cylinders in one of said members, pistons reciproeating in v`said cylinders, a discharge port and return port in the other of said members cooperating with said cylinders, each cylinder adapted to communicate with said discharge port 'during the pressure stroke of its cooper-l ating piston and with said return port during the suction stroke of its piston, said ports and cylinders being so related that communication is maintained between each cylinder and said return port until its cooperating piston has started a pressure stroke.

44. The combination of a casing constituting a liquid reservoir, a rotary multiple piston pump in said casing wit-hin the body of liquid therein, and a housing substantially enclosing said pump and excluding the body of liquid therefrom.

45. The combination of a casing constituting af liquid reservoir, a rotary multiple piston variable displacement pump therein, a partition separating said pump from the body of liquid therein and means projecting through said partition for varying pump displacement.

46. The combination of a casing constituting'a liquid reservoir, a rotary multiple piston variable displacement pump therein, a pump housing including a partition separating said pump from the body of liquid therein, means projecting through said partition for varying pump displacement, and means for excluding liquid from said pump housing.

47. The combination of a casing consti- L tuting a liquid reservoir, ,a rotary multiple piston pump therein with its axis of rotation below the'. liquid level in said reservoir, a pump housing separating said pump from the body of liquid in said casing, and inea-ns for excluding liquid from said pump housing.

48. The combination of'a-casingponstituting a liquid reservoir, a pump within a body of liquid therein, a artition separating said pump from the bo y of lliquid in said casing, a pintle projecting through said partitio and having fluid passages leading to said pump, circulating passages connected with said pintle passages, and valve controlled passages between said pintle passages and the body of liquid in said casing.

49. The combination of a casin constitutin a liquid reservoir, a shaft t erein, a varia le displacementpump in a body of liquid therein, a partition separating said pump from the body of liquid in said casing, an element projecting through said partition and having assages vconnected with said pump, a mem er rockable on said shaft and maaien said rst named passages between said pump and support. 1

5l. The combination of a variable displacement pump, a member movable to vary pump displacement and having passages communicating with said pump, a ixed support for said member having uid passages-therein, a valve in said member for controlling communication between the passages therein and those in said support, a uid reservoir, and means connectin said reservoir with a passage in said mem er between said pump and valve.

52. rlhe combination of a variable displacement pump, circulating passages fed by said pump, valve mechanism for controlling the direction of fluid flow in said passages, and means for simultaneously operating said valve mechanism and for regulating pump displacement, said valve mechanism including means for short circuiting said pump and for blocking said passages when said regulating means is in zero displacement position.

53. In a hydraulic machine the combination of two rotary members, a radial serie-s of piston and cylinder assemblies between said members, easy assembly having a cross-head, a series of tangential reaction faces on one of said members, one opposite each crosshead, a roller bearing between each cross-head and reaction face, and stops on said reaction 57. The combinationfwith a variable disl placement pump, of a shaft having passages for connection with two sidespf a hydraulic circuit, a member rockable on said shaft to vary pump displacement, discharge and return passages in said member for connecting said pump with said irst named passages, respectively, a valve for controlling communication between said first named and said last named passages, a reservoir, and a passage connecting said reservoir with said return passage independently of said lirst named passages.

ln witnesswhereof', we hereunto subscribe our names this, 1st day of March, 1926.

WALTER FERRIS. JOHN P. FERRIS.

faces and cross-heads for limiting the travel of said roller bearings therebetween.

54. The combination with a variable displacement pump, of a shaft having passages therein for connection with the opposite sides of a hydraulic circuit, a member rockable on said shaft to vary pump displacement, passages in said member for connecting the pump with said first named passages, respectlvely, a liquid reservoir, and passages separately connected with said reservoir for supplying liquid to said pump independently of said first named passages.

55. The combination with a variable diS- placement pump, of a shaft having passa es therein for connection with the opposite si es of a hydraulic circuit, a member rockable on said shaft to vary ump displacement, passages in said mem er for connecting said pump with said rst named passages, respectively, a liquid reservoir, passages connecting said pum with said reservoir, inde-` pendently of sai first named passages, and separate check'valves for controlling said last named passages. l

56. The combination with a variable displacement pump, of a shaft having passages therein for connection with the opposite sides'of a hydraulic circuit, a member rockable on ysaid shaft to vary pump displacement, passages'-lin said member connected i.

said pump, a valve controlling communi- .fo-ati'on between said first named passages and lastznamed 'passages to thereby control soA 

